ML19327A071
| ML19327A071 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 07/18/1980 |
| From: | Heider L VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-80-17, WVY-80-102, NUDOCS 8008010124 | |
| Download: ML19327A071 (5) | |
Text
3-g VERMONT YAN KEE NUCLEAR POWER CORPORATION SEVENTY SEVEN GROVE STREET WVY 80-102 RUTLAND, VERMONT 05701 REPLY TO:
ENGINEERING OFFICE TURNPIKE RCAo WESTBORO. M ASSACHUSETTS 01581 TELEPHONE 6 8 7-366-90 t t July 18, 1980 United States Nuclear Regulatory Commission Office of Inspection and Enforcement Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Attention:
Mr. Boyce H. Grier
Reference:
(a) License No. DPR-28 (Docket No. 50-271)
(b) USNRC letter to VYNPC, dated July 3,1980; IE Bulletin 80-17 (c) VYNPC letter (WVY 80-98) to USNRC, dated July 8, 1980 (d) USNRC letter to VYNPC, dated July 9, 1980.
(e) VYNPC letter (WVY 80-100) to USNRC, dated July 13, 1980
Subject:
Response to IE Bulletin 80-17; Failure of Control Rods to Insert During Scram
Dear Sir:
As a result of a sicuation at Brown's Ferry Unit No. 3, wherein a number of control rods failed to scram following a manual scram attempt, References (b) and (d) required that Vermont Yankee perform certain scram tests and report the results of the tests to the NRC within 5 days thereafter.
In accordance with that directive, the following information is submitted in response to Bulletin Items 2 and 3.
All other Bulletin items have been addressed in References (c) and (e).
Item 2 "Within the i.axt 20 days,~ perform one manual and one automatic scram in that order at normal operating temperature and pressure and with more than 50 percent of the rods fully withdrawn, and obtain the following information on each scram:
a)
All rod insert times and as many individual rod scram times as practicable."
80 08010/J2il
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Unitcd Stat c Nuclesr R;gulctory Commission July 18, 1980 Att:nticn:
Mr. Boyca H. Crist Page 2
Response
The automatic and manual scrams were initiated from essentially identical rod patterns. Tha pattern consisted of 73 of 89 rods at positions other than full in; 57 of the 73 rods were fully withdrawn. 51 of the 57 rods were monitored for scram times.. The. slowest rod of those monitored to reach. the full in position was considered the "all rod insertion time".
All rods were verified to be at position 00 following each of the scram tests.
Results were:
Manual Scram Test Auto Scram Test Avg. (51 rods) 87.8% insertion time 2.377 sec 2.388 see "All rod insertion time" 3.208 sec 3.200 see b)
" Voltage at the scram solenoid valve buses to verify that these solenoids are de-energized upon receipt of scram signal."
Response
Voltage readings taken during both the manual and automatic scram tests verified that the,,.tes de-energized properly.
c)
" Verify that scram valve air is relieved through the backup valves and that the backup valves are fully open and remain open during the presence of a scram signal."
Response
Proper operation of the backup scram valves was verified for both the manual and automatic scram test.
d)
" Measure fill time of the instrument volume from scram initiation to closure of the scram instrument volume high level alarm switch, to closure of the rod withdraw block switch on the instrument volume and to the closure of the scram instrument volume reactor scram switch."
Response
Times measured with a strip chart recorder for each scram were:
"Hi Level Alarm (sec)
Rod Block (sec)
Scram A (sec)
Scram B (sec)
Manual Scram 28.3 40.4 62.9 61.4 Auto Scram 31.8 43.8 66.8 69.8 e)
" Measure vent and drain valves opening and closing times utilizing the valve stem mounted switches.
This measurement may be made independent of the scrams."
Response
Travel times for each of the valves were measured three times independent of the scram.
Rather than use the position switches to determine travel
'.- Unitdd St t:3 Nuciocr R3guictory Commi0sien July 18,' 1980
- e
.Att1nti:n:
Mr. Boyca H..Grict Paga 3 time, a'stop watch was used to measure actual travel time locally at the
~
valve. The average times are listed below.
Individual times were all within L 'second of the averages.
Open to Close (sec)
Close to Open (sec)
Drain 4.8 6.8 Vent A 7.8 3.9 Vent B 4.3 10.4 f)
" Measure the delay time from scram initiation to closure of the SDV vent and drain valves utilizing the stem mounted position switches."
Response
A strip chart recorder was used to monitor delay times utilizing the stem mounted position switches on each of the valves.
The times measured for each scram were:
Scram Signal to Closure of (sec)
Drain Valve Vent Valve (A)
Vent Valve (B)
Manual Scram 2.7 10.6 5.0 Auto Scram 2.7 10.6 5.0 g)
" Sample water from the instrument volume discharge af ter each scram for particulates."
Response
Filterable solids were measured using.45 micron millipore filters for samples collected from the instrument volume af ter each scram.
Results were:
Filterable Solids (ppm)
Manual Scram 20.7 Auto Scram 29.7
'h)
" Measure the time to drain the SDV down to a repeatable reference level."
Response
After a suitable delay time (to reach system stability), the scram was reset and the time was measured to drain the SDV from scram reset to the point where the high level alarm cleared. Times for each scram were:
Scram Reset to SDV Hi Level Reset Manual Scram 4.1 minutes Arto Scram 3.9 minutes i)
" Monitor the SDV and associated piping for residual water."
U2itid Stat:0 Nuciccr Regulatory C:mmissisn July 18,' 1980 3
Attentico:
Mr. Boyc2 H. - Grisr Paga 4
Response
Following the manual scram, and both before and af ter the automatic scram, the SDV was monitored for water. Af ter all tests, a small accumulation of water was found in one of the 6" SDV pipes.
Further evaluation indicated that the maximum water depth was -- 0.8" tapering out in each direction to -w 0.0" within six feet.
The total amount of water represents 4 0.3% of the total volume in the north SDV header.
This small amount of water is of little significance and does not impair the safety function of the SDV.
Measurements taken confirm that the bottom of this small portion of piping is at a lower point than the 2" drain to the SDV instrument volume. UT monitoring will continue to be performed at this system low poin t.
It is expected that the water will eventually evaporate.
j)
" Verify that the ten (10) second delay on scram reset is functioning properly to prevent resets of momentary scram signals."
Response
Prior to both the manual and automatic scram, the ten (10) second delay on scram reset was verified thru normal station procedures to be functioning properly.
k)
" Compare the results of the two sets of data taken above with each other and'with any previcusly obtained data."
Response
Comparison of the above data shows little, if any, significant difference between the results of the manual and automatic scrams.
Scram times for each of the tests were compared with previously collected data and were well within the normal range for scram times. A review of pre-op and original start-up tests failed to uncover any data which could be used to compare with the results of this test.
Item 3 "At the conclusion of the scram tests and all other scrams, verify that all vent lines on the SDV are functional.
Verify that there is no significant amount of water in the SDV and associated piping."
Response
See our response cu Item i) above.
Subsequent to tra asmitting our last submittal, Reference (e), it was identified that our response to Item 4e requires modification.
The necessary prel*minary training was completed on July 11, 1980 for all but four licensed operacors who were not on shif t during the ten day in te rval.
Those four operstors each received their training on their next scheduled work day, Jeiy 14, 1980.
'Unitcd Stctss Nucisar Rigulctory Commiscien July 18, 1980 Attsntient Mr. B:yca H. Grisr PEgo 5 Within the prescribed 30 day timeframe all available information regarding the Brown's Ferry incident will be discussed with station operators and they will be fully trained in procedures revised as a result of the
' incident.
The following information is submitted in response to your request for estimates of manpower expended in the research and subsequent performance of actions associated with this Bulletin:
Manpower Requirements Hours Bulletin Response 680 Corrective Actions N/A It should be clearly understood that this information is not adequate to enable a value/ impact assessment. The cost of equipment, the cost of additional resources to perform additional work, and cost of installation are also necessary.
In addition an adequate determination of the safety improvement as a result of this document needs to be included.
We trust that the above supplied information, along with that previously submitted in References (c) and (e), satisfactorily completes the reporting requirements of the subject Bulletin. However, should you desire additional information, please contact us.
Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION N
L. H. Heider Vice President RJW/jgh COMMONWEALTH OF MASSACHUSETTS)
)ss COUNTY OF WORCESTER
)
Then personally appeared before me, L. H. Heider, who, being duly sworn, did state that he is a Vice President of Vermont Yankee Nuclear Power Corporation, that he is duly authorized to execute and file the foregoing request in the name and on the behalf of Vermont Yankee Nuclear Power Corporation, and that the statements therein are true to the best of his knowledge and belief.
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,g Robert H. Groce Notary Public
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j My Commission Expires September 14, 1984 Y,v. g.g a. :
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